Duffy studied painting at Pratt Institute and received a BFA in art history and painting from Carnegie Mellon University. Upon graduation his drawing skills earned him a technical illustrators position in the Department of Vertebrate Paleontology at the American Museum of Natural History, New York. A decade of freelance illustration projects followed creating original works for novel covers and award-winning young adult and children's books.

In 1998 Duffy set up a studio in Connecticut to focus primarily on portraiture with the space and light required. His reputation and expertise garnered commissions to paint the official portraits of many distinguished and accomplished citizens including the leaders of American Universities, Colleges and Corporations, public servants in US Federal Government and the State and Federal Judiciary . In 2007 Duffy was selected to paint the official portraits of the current and 4 past Secretaries of the US Department of Housing and Urban Development(HUD) and

2005-2012 Adjunct Professor/Lecturer in the Department of Fine Arts, Paier College of Art, Hamden, Connecticut

2012 Lundbeck Fellowship in the Humanities and Artist-in-Residence, University of Limerick, School of Medicine, Limerick, Ireland.

Duffy's work has been included in group exhibitions in New York, Washington, DC, Miami, Berlin, Florence, Dublin, Belfast and London and is in the permanent collections of United States, National Portrait Gallery and The Royal Hibernian Academy, Dublin.